In Patent Document 1, a gallium nitride single crystal growth process is disclosed. According to this process, a gallium nitride single-crystal growth process enabling oxygen to be taken in as an n-type dopant is afforded. In this process, using a seed crystal having the plane apart from the c-plane on the front side (top side), while a source gas including raw-material gallium, raw-material nitrogen, and oxygen for doping is supplied, gallium nitride crystal is vapor-deposited, with the front side apart from the c-plane being kept intact, to dope oxygen into the gallium nitride crystal through the front side. In another instance, using a seed crystal having the c-plane on the front side, while a source gas including raw-material gallium, raw-material nitrogen, and oxygen for doping is supplied, gallium nitride crystal is vapor-deposited along the c-axis, with a facet plane apart from the c-plane being created and the facet plane being kept intact, to dope oxygen into the gallium nitride crystal through the facet plane.
Non-Patent Document 1 describes characteristics of pin diodes. In these diodes an (undoped, n ˜3×1016 cm−3, 3 micrometers) gallium nitride epitaxial film and a (Mg-doped, p˜1×1017 cm−3, 0.3 micrometers) gallium nitride epitaxial film are fabricated by metalorganic vapor deposition onto a gallium nitride freestanding substrate, and on the back side of the gallium nitride freestanding substrate, an ohmic electrode for the n-type is fabricated, and on the front side of the epitaxial film, an ohmic electrode for the p-type.
Patent Document 1: Japanese Unexamined Pat. App. Pub. No. 2002-373864. Non-Patent Document 1: Irokawa et al., Applied Physics Letters, Vol. 83, 15 Sep. 2003, pp. 2271-2273.